Various devices have been proposed for reducing engine smoke by injecting water into a combustion chamber of an engine to control intra-chamber temperature. Such water injection devices typically have a single nozzle type injection device, which injects both fuel and water. The structure of these single nozzle type injection devices is highly complicated. In addition, since water and fuel are injected simultaneously, corrosion often occurs. Further, water is also injected at a high pressure together with the fuel, and therefore, the fuel system is overloaded, shortening the life expectancy of the engine. Still further, the roles of water and fuel are different within the combustion chamber. Thus, there is a technically restricting problem in that the time when fuel is injected and the time when water is injected have to correspond with each other.
Another device for introducing water into the combustion chamber is a suction tube (as compared with the direct water injection through the nozzle). This method has an advantage in that a sudden variation in temperature in the combustion chamber can be prevented. However, such a water injection device has its own limitations, such as the injection time and injection amount of the water particles.